1. Field of the Invention
This invention relates generally to the field of time division multiplexing. More particularly to this invention relates to a method and apparatus for assigning time slots within a frame of time slots in a time division multiplexer capable of dynamic bandwidth allocation.
2. Background of the Invention
In time division multiplexers, a frme of time slots is repeatedly transmitted with one or more time slots being used to provide the bandwidth needed by each of the multiplexer channels. When such a multiplexer is required to dynamically create and tear down connections (channels) of varying bandwidth, the proces of doing so can create gaps or large areas of consecutive time slots that are unavailable for allocation in the frame. This phenomenon sometimes causes inefficiencies and also sometimes results in the inability to create a connection even though adequate bandwidth exists within the frame. This is because although adequate bandwidth may exist, the location of the time slots within the frame may be such that allocation of the available time slots is impossible due to constraints in buffer size. That is, if the available time slots are assigned, a buffer overflow or underflow will result. One solution to this problem might be to redistribute the entire frame every time a new connection is required. However, this proposed solution requires a substantial level of computing effort, a rearrangement of the frame on each node in the network and an additional delay for each connection setup. Accordingly, the solution proposed by the present invention, while not guaranteed to be optimal, provides a practical mechanism for accommodating new call set-ups under most circumstances.